Ever since 1774, when Benjamin Jesty vaccinated his wife with cowpox to protect her from smallpox, vaccines have been at the front lines of our battles against infectious diseases. Now could be their heyday, with some accusations about vaccine safety finally proven false, and more vaccines being developed and even given to older and older patients.
Martha Folmsbee, Ph.D., staff scientist in the scientific and laboratory services department of Pall, will be among the speakers at IBC’s “Vaccine Production Summit” in Boston in June. She will be discussing how filters behave differently under different conditions, so that although filters are tested by their manufacturers, those tests may not be directly relevant if manufacturing conditions differ from test conditions.
According to Dr. Folmsbee, “no filters are absolute for every possible solution,” rather, a specific filter must be chosen for each application. In addition, filter ability and retention can be inversely proportional, so a happy balance must be found. Manufacturers often opt for filtration products that can filter their solutions more quickly, but they need to be aware that by doing so they might be compromising sterility in some cases.
In terms of vaccine production, Dr. Folmsbee warns that adjuvants, often oils, surfactants, and liposomes, can decrease the surface tension of a solution. This lower surface tension can diminish the bacterial retention of any given filter. Adjuvants can also clog filter pores, further reducing their bacterial retention. Some adjuvants—like aluminum salts, some liposomes, and microparticles—may be larger than some bacteria, making filtration of the final solution an ineffective method of terminal sterilization. In such cases each component must be filtered or otherwise purified further upstream in the process, and then the components can be combined aseptically.
Intercell has developed a transcutaneous patch technology for delivering vaccines to the skin. In contrast to the currently used intramuscular injections, which are invasive and allow vaccines to travel to distal lymph nodes and create systemic side effects like soreness and fever, this method allows for a local administration, according to CSO Larry Ellingsworth.
“Skin is a good target for vaccination if you can get the vaccine efficiently delivered.” Skin has a high density of dendritic and Langerhans cells, so lower doses of vaccines can be administered to achieve the same response as injected formulations.
Delivery relies on pretreatment of the skin with the company’s Skin Preparation System, a mild abrasive that removes the stratum corneum to enhance uptake of the vaccine. “It took a lot of time and development cost” to ensure that this system didn’t hurt and to make it more attractive than a needle and enhance compliance, Dr. Ellingsworth says. Intercell uses the heat-labile enterotoxin (LT) from Escherichia coli as an adjuvant. LT induces a potent enhancement of both T-cell and antibody responses but is too toxic to be administered orally or intranasally.